Gyroscopes



United States Patent 3,396,587 GYROSCOPES John Thomas Gresham, Skillman,N.J., assignor to FMC Corporation, New York, N.Y., a corporation ofDelaware No Drawing. Filed Apr. 1, 1966, Ser. No. 539,301 3 Claims. (Cl.74-5.5)

This invention relates to floated control instruments, particularlyfloated gyroscopes in which the flotation fluid is an organic mercurycompound.

A floated gyroscope is one in which the rotor is encased in a float. Thedensity of the flotation fluid is chosen to match the density of thefloat. Such a construction enables the float to rotate about its pivotwith an exceedingly low degree of friction. The gyro fluid also protectsthe assembly from shock, provides a damping function and a heat transfermedium which serves to dissipate heat generated by the rotor. Where theclamping efl ect on the precession of the float is developed primarilyby the fluid itself, it is generally preferable that the fluid exhibithigh viscosity. However, when damping is not desired or Where electronicor orifice damping is employed, low viscosity liquids are preferred.

In addition to the above described use in a single gyroscope, a gyrofluid may be employed in a system wherein one or more gyros oraccelerometers and associated equipment are mounted on a platform whichis floated in the liquid. Fluids for this application are usually dense,low viscosity liquids for flotation only.

Liquids suitable for use in gyroscopes must possess certain criticalphysical characteristics and in this connection it is essential that theliquids exhibit high density, at least about 1.6 g./ml. The higher thedensity the more useful the fluid, since this permits more inertia to bebuilt into the rotor without imposing higher loads on the pivot hearing.A higher density fluid by the same token allows size reduction at thesame amount of inertia (and sensitivity of the gyro). A second parameterof such liquids is that they exhibit Newtonian behavior, i.e., beindependent of the shearing rate. Preferably the liquid also should berelatively insensitive in viscosity to tem perature variations. It must,of course, remain serviceable over the operational temperature range ofgyroscope. Finally, it is essential that the liquid remain stable Whilein use since any degradation or breakdown may form decompositionproducts which may corrode the metal components and parts of thegyroscopes.

Because of the stringent specifications required of gyro fluids, it hasbeen exceedingly dificult to find suitable materials. Those in generaluse today are based on fluorocarbons since these constitute one of themore stable classes of fairly dense liquid compounds. The high viscosityfluids are normally telomers of CFCl=CF and CFBr=CF having densities ofabout 1.7 and 2.4 g./ml., respectively. Where low viscosity liquids arecalled for, low molecular ends of the telomerization product of theolefins are sometimes employed; a volatile fiuorinated cycloether havingthe empirical formula C F O and a density of 1.7602 g./ml. at 25 C. isalso a preferred choice. Halogenated hydrocarbons other than fluorinatedhydrocarbons have been conisdered but are generally unsatisfactorybecause of their reactivity with metals and sensitivity to hydrolysisand thermal decomposition.

With a view to developing improved gyro fluids We now have discovered aclass of organic mercury com pounds which exhibit the aforesaidparameters to a marked degree and the provision of these compounds andtheir use as gyro fluids constitute the principal object and purpose ofthis invention. Other objects and purposes will become manifestsubsequently.

The organic mercury compounds as contemplated herein aredi(alkylmercuri)alkanes wherein the alkyl moiety is desirably methylwhile the alkane portion is preferably selected from the classconsisting of linear alkanes having from 1 to 2 carbon atoms and acycloalkane as represented by cyclopropane. The compounds can bevisualized more readily by reference to the following general formula:

HgCHa wherein Z designates an alkane hydrocarbon residue which may be alower linear alkane such as CH or CH CH and a cycloalkane such as -CHCHThe novel organic mercurials herein are prepared by reacting a metalalkyl with an alkylmercuric halide and separating the resultingdi(alkylmercuri)alkane from the metal halide by-product. Purification ofthe organic mercury compound can be achieved by such well knowntechniques as sublimation, distillation, crystallization, chromatographyor combinations thereof.

The following non-limiting examples are illustrative of how thecompounds of the invention can be obtained.

Example 1.Dz'(methylmercuri) methane HgCHa HECHQ To 0.1 mole ofdi(iodomercuri)methane in dry tetrahydrofuran is added 0.25 mole ofmethyllithium, the temperature being maintained at about 0 C. during theaddition. After stirring for several hours the resulting mixture isallowed to warm up to room temperature. The di- (methylmercuri)methaneis then isolated using any of the purification techniques commonlyemployed in the art.

The di(iodornercuri)methane is prepared following a modified procedureof J. Sakurai, J. Chem. Soc., 39, 485 (1881): Thus, a stirred mixture of1 mole of mercury, 0.15 mole of methylene iodide and l g. of mercuriciodide is irradiated with a sun lamp. When the slurry solidifies,1,2-dimethoxyethane is added and the mixture irradiated overnight. Thesolids are mixed with 10% potassium iodide to remove mercuric iodide andWashed with water and acetone. Bis(iodomercuri)methane is obtained byrecrystallization of the crude product from hot methylene iodide.

Example 2.-1,1-di(methylmercuri) ethane HgCH;

CHSCH HgCHa This compound is prepared following the procedure of Example1 'but substituting ethylidenedimercuric chloride, CH CH (HgCl) fordi(iodomercuri)methane.

The requisite ethylidenedimercuric chloride is obtained using thesynthesis described in J. Org. Chem., 29, 2742 (1964): g. of borontrifluoride etherate in 250 ml. of tetrahydrofuran is added undernitrogen atmosphere over a period of /2 hour to a stirred slurry of 15.8g. of sodium borohydride in ml. of diethylene glycol and 250 ml. oftetrahydrofuran cooled in an ice bath. The mixture is stirred 20 minutesat 20 C., cooled in an ice bath and 92 g. (0.5 mole) ofdibutylvinylboron-ate is added in /2 hour. After two hours at 20-25, themixture is cooled in ice and ml. of n-butanol added in one hour. At theend of 30 minutes at room temperature, hydrogen evolution had ceased.The mixture is cooled in ice and treated 3 with 500 ml. of water andthen 271 g. of mercuric chloride.

With cooling, a solution of 40 g. of sodium hydroxide in 200 ml. ofwater is added dropwise at such a rate that the yellow color of mercuricoxide remains discharged. After filtration overnight on a large Buchnerfunnel to remove mercuric chloride, the filtrate is dilute-d with aliter of water and concentrated at 20 mm. to remove most of the organicsolvents. The crude product is collected by filtration and washed withacetone. Additional product is obtained by diluting the mother liquorsto about 3 liters, filtering, and extracting the mercurous chlorideprecipitate with dimethylsulfoxide followed by filtration of thesolution diluted with acetone and water.

Example 3.1,2-di(m'ethylmercuri)cyclopropane HaCHg HgCHa HO-CH Hz Thiscompound is prepared by adding methylmercuric bromide to the Grignardreagent of 1,2-dibromocyclopropane. The unreacted magnesium is removedfrom the reaction mixture after which two equivalents of methylmercuricbromide are added in small portions keeping the temperature at about -10C. At the end of the addition stirring is maintained for several hourswhile allowing the reaction mixture to come to room temperature. The1,2- di(methylmercuri)cyclopropane is then isolated from the reactionmixture.

The Grignar'd reagent of 1,2-dibromocyclopropane is prepared by asynthesis similar to that described in J.A.C.S., 82, 6375 (1960). Inthis procedure 11 g. of 1,2- dibromocyclopropane is added with stirringto 40 ml. of anhydrous ether and 2.9 g. of 99.99% magnesium. After thereaction has ceased, a quantity of magnesium remains as residue.

1,2-dibromocyclopropane is a known chemical material obtained by thebromination of cyclopropene in accordance with a procedure set forth inJ.A.C.S., 82, 6375 (1960). This method involves introducing a stream ofcyclopropene and nitrogen into a solution of carbon tetrachloride andbromine at 0 until the bromine color is dis wherein Z designates analkane hydrocarbon residue selected from the class consisting of loweralkane and cyclopropane.

2. A gyroscope comprising a gyroscope float suspended in anorganomercury compound of the formula:

HgOHa wherein Z designates an alkane hydrocarbon residue selected fromthe class consisting of lower alkane and cyclopropane. 3. A guidancesystem containing a platform suspended in an organomercury compound ofthe following formula:

wherein Z designates an alkane hydrocarbon residue selected from theclass consisting of lower alkane and cyclopropane, said platform havingmounted thereon at least one gym and associated equipment.

No references cited.

C. J. HUSAR, Primary Examiner.

1. A CONTROL SYSTEM COMPRISING A CONTROL ELEMENT IN OPERATIVE CONTACTWITH A HIGH GRAVITY FLUID WHICH IS AN ORGANOMERCURY COMPOUND OF THEFOLLOWING FORMULA: